1. Field of the Invention
The present invention relates to a device and method for suppressing noise caused by stimulated Brillouin scattering (SBS) which is generated when signal light propagates through an optical fiber.
2. Related Background Art
A technology for processing wavelength conversion and waveform shaping of high-speed signal light using a nonlinear optical effect, which is generated when a high power light propagates through an optical fiber, has been proposed. Such a technology is described in, for example, Japanese Patent Application Laid-Open No. 8-54653, G. P. Agrawal, “Nonlinear Fiber Optics”, Academic Press, and P. O. Hedekvist et al., “Noise characteristics of fiber-based optical phase conjugators”, Journal of lightwave technology, vol. 17, No. 1, January, 1999. However, in the case that this technology is used, SBS is generated when the intensity of the signal light is too high. SBS is a phenomena whereby propagation light receives a backward scattering effect by the propagation light itself, when the propagation light induces acoustic vibrations at coupling in the optical fiber. The scattering light also becomes a seed and prompts the next scattering. So, when the intensity of the propagation light exceeds a certain threshold, the scattering lights increase exponentially.